In order to start or stop an outboard motor, an ignition switch provided to an outboard motor main body or provided in an operation cabin has been conventionally used. Concretely, by inserting a key into the ignition switch, and rotating the ignition switch in stages, the ignition is turned on, and then a start SW is turned on, which starts the outboard motor.
In recent years, a demand for improving a security of a boat and an outboard motor has been increasing. However, in the outboard motor which is started by the ignition switch described above, it cannot be always said that the perfect security is provided. Therefore, it can be considered that, with respect to the boat and the outboard motor as well, an engine start system in which a key is not required as disclosed in Patent Literature 1, for example, is employed to improve the security. In Patent Literature 1, only when an encryption code received from a portable machine coincides with a collation code, a steering lock is unlocked so that an operation is allowed, which enables to improve the security.